1. Field of the Invention
The present invention relates to memory devices and more particularly, to an apparatus and method for reading data from a disk type memory.
2. Description of the Related Art
Generally, an optical disk drive, which is one example of disk drives for disk type memories, rotates a recording medium called an "optical disk". The optical disk is rotated at given revolution speed (i.e., a given number of revolutions per minute) while an optical-pick-up reads from or writes to the optical disk. When there is defective (or unreadable) data on the disk due to dust or damage to the recording media, the data cannot be accurately read using the given revolution speed. In order to read the defective area, the revolution speed is reduced until the data can be read (i.e., to perform error correction). In a conventional optical disk drive, error correction is performed by retry operations. Thus, if defective data is encountered during the reading of data, the pick-up is moved to where the defective data exists, and the number of revolutions of the disk is reduced. The reading operation is restarted at this position to read the defective data, i.e., to perform error correction. If it is impossible to achieve error correction with the reduced revolution speed, the above operation is retried in a subsequent manner.
The conventional optical disk drive performs a retry operation to read defective data and, depending on the extent of defective data, the number of retry operations may be quite large. For this reason, the conventional optical disk drive has an disadvantage in that reading speed is decreased when defective data is detected due to the retry operations.